A construction machine such as a hydraulic excavator includes a hydraulic driving system and a plurality of actuators and drives the actuators by introducing pressure oil from the hydraulic driving system to the actuators. Known as the hydraulic driving system of the construction machine configured as above is, for example, a hydraulic driving device of PTL 1.
The hydraulic driving device of PTL 1 includes three pumps. By introducing operating oil from these three pumps to various actuators such as a traveling motor, a turning motor, a boom actuator, an arm actuator, and a bucket actuator, the hydraulic driving device can perform traveling, turning, lifting and lowering of a boom, bending and extending of an arm, and excavating and dumping of a bucket. Those actuators are provided with corresponding control valves, and each of the control valves changes a state of supplying the operating oil to the corresponding actuator. Those control valves constitute three control valve groups, and a first control valve group is connected to a first pump. A second control valve group and a third control valve group are connected to a second pump and a third pump, respectively.
The first control valve group includes a turning control valve, a boom control valve, an arm control valve, and a bucket control valve. The second control valve group includes an arm control valve, a boom control valve, and a bucket control valve. The third control valve group includes an arm control valve. By operating lever devices correspondingly provided at the control valves of the second and third control valve groups, pilot pressure is input to the control valves of the second and third control valve groups. The control valves of the second and third control valve groups operate by the pilot pressure to supply the operating oil, ejected from the second and third pumps, to the corresponding actuators. Further, by operating the lever devices correspondingly provided at the control valves of the first control valve group other than the turning control valve, pilot pressure regulated by an electromagnetic control valve is input to the control valves of the first control valve group other than the turning control valve. When the turning control valve operates, the pilot pressure input to the control valves of the first control valve group other than the turning control valve is blocked. Thus, when the boom, the arm, or the bucket is operated at the same time as the turning operation, the operating oil ejected from the third pump can be supplied only to the turning motor.